The presence of mercury in produced natural gases often necessitates the use of activated carbon beds to absorb and remove the mercury from the gas. For example, U.S. Pat. No. 3,194,629 discloses a process for removing mercury from a gas contaminated with mercury comprising passing the gas over activated carbon impregnated with sulfur. Ordinarily the carbon will have deposited on it sulfur in dispersed form so that the sulfur will react with the mercury to form mercuric sulfide which is more easily fixed on the absorbent bed and which poses less of a threat to equipment located downstream. This equipment might otherwise be damaged seriously due to corrosion by the mercury. Particularly threatened are the aluminum heat exchangers used in large volume LNG plants. Depending, of course, upon the concentration of mercury in the gas treated, the adsorbent containing sulfur, mercuric sulfide and mercury eventually must be removed and replaced by fresh absorbent. Disposal of this spent sorbent material can pose a problem. It is not safe to bury the material because ground waters seeping through the buried material may become contaminated and their continued percolation to the eventual contamination of large bodies of water. The mercury present in the discarded adsorbent may also be of some value commercially and it is therefore desirable to reclaim it if at all economically possible.
A primary object of this invention therefore is to provide an economical means of recovering mercury from a spent carbon based absorbent.
Another object of this invention is to provide a method of decontaminating the waste absorbent so it can be discarded without being a hazard to human health or welfare.